High efficient assimilation of NO₃⁻-N with coproduction of microalgal proteins by Chlorella pyrenoidosa / 生物工程学报

The aim of this study was to establish a novel technology using microalgae for NO₃⁻ removal from high concentration wastewater and conversion to algal proteins. The effects of cultivation modes and illumination modes on the biomass yield, NO₃⁻ assimilation rate and algal protein yield were first investigated in shaking flasks for mixotrophic cultivation of Chlorella pyrenoidosa, and subsequently the scale-up verification in 5-L photo fermenter was successfully conducted. Fed-batch cultivation without medium recycling was the best cultivation mode in shaking flask system, in which the highest biomass yield (35.95 g/L), the average NO₃⁻ assimilation rate (2.06 g/(L·d)) and algal protein content (up to 42.44% of dry weight) were achieved. By using a staged increase of light intensity as illumination modes, the specific growth rate of cells could be significantly promoted to the highest (0.65 d⁻¹). After a 128-hour continuous cultivation in a 5-L photo fermenter, the highest biomass yield and the average NO₃⁻ assimilation rate were reached to 66.22 g/L and 4.38 g/(L·d) respectively, with the highest algal protein content at 47.13% of dry weight. Our study could provide a photo fermentation technology of microalgae for highly efficient treatment of waste industrial nitric acid and/or high concentration nitrate wastewater. This microalgae-based bioconversion process could coproduce protein-rich microalgal biomass, which facilitates the resource utilization of these type wastewater by trash-to-treasure conversion.

Development of Fed-Batch Cultivation Strategy for Efficient Oxytetracycline Production by Streptomyces rimosus at Semi-Industrial Scale

ABSTRACTOxytetracycline (OTC) production byStreptomyces rimosus was studied in batch and fed-batch cultures in shake flask and bioreactor levels using semi-defined medium. First, the effect of glucose concentration on OTC production and growth kinetics was studied intensively. The optimal glucose concentration in the medium was 15 g/L. Higher glucose concentrations supported higher biomass production by less volumetric and specific antibiotic production. Based on these data, cultivations were carried out at semi-industrial scale 15 L bioreactor in batch culture. At bioreactor level, cell growth and OTC production were higher compared to the shake flask culture by about 18 and 38%, respectively. During the bioreactor cultivation, glucose was totally consumed after only 48 h. Thus, the fed-batch experiment was designed for mono-glucose feeding and complete medium feeding to increase the OTC production by overcoming carbon limitations. The results showed that the fed-batch culture using constant glucose feeding strategy with rate of 0.33 g/L/h produced 1072 mg/L. On the other hand, feeding with complete medium resulted in 45% higher biomass but less OTC production by about 26% compared to mono-glucose fed culture. A further improvement in this process was achieved in by keeping the dissolved oxygen (DO) value at 60% saturation by cascading the glucose feeding pump with the DO controller. The later feeding strategy resulted in higher antibiotic production, reaching 1414 mg/L after 108 h.

Production of Inulinase by Free and Immobilized Cells of Penicillium funiculosum p.36

The aim of this work was to optimize the growth conditions and continuous production of the enzyme using free and immobilized cells of inulinase by Penicillium funiculosum. The highest yield of enzyme (163.5U/mL) was obtained when the culture was incubated at 27oC and 200 rpm for 96h in a fermentation medium containing both inulin and peptone as sole carbon and nitrogen source, respectively. When the cells of the P. funiculosum were immobilized on different carriers, especially linen fibers, their production ability was successfully maintained for seven successive batches. When the fermentation was carried out using inulin juice prepared from Jerusalem artichoke tubers (in place of pure inulin), inulinase production could be sustained till the second cultivation batch of the P. funiculosum immobilized on linen fibers, yielding 122 U/mL enzyme. Results proved the feasibility of using crude inulin juice as a simple and economic carbon source for the production of inulinase.

Glucose concentration affects recombinant interferon α-2b production in Escherichia coli using thermo-induction system.

In the present work, a recombinant Escherichia coli strain was used for the production of interferon α-2b in both shake flask and in bioreactor. The first part of this research was focused on the investigation of the effect of glucose concentration on the kinetics of cell growth, recombinant protein production and acetate formation. In general, glucose supplementation to culture medium enhanced cell growth when added in concentration between 0-20 g/L. Further increase in glucose level reduces biomass production and enhances acetate accumulation in culture. The results clearly demonstrated that maximal interferon production of 27.7 mg/L was achieved in culture supplemented with 20 g/L glucose. Further improvement in recombinant interferon production process was also achieved by scaling up from shake flask to 16-L stirred tank bioreactor. The maximal volumetric interferon production in bioreactor batch culture was 44.5. mg/L after only 6 hours.

INFLUENCIA DE LA AIREACIÓN EN LA ACTIVIDAD FERMENTATIVA DE Kloeckera apiculata DURANTE LA FERMENTACIÓN DE JUGO DE MANZANA / Influence of Aeration in the Fermentative Activity of Kloeckera apiculata during Fermentation of Apple Juice

Se ha estudiado la influencia de la aireación en la actividad fermentativa de Kloeckera apiculata RIVE 9-2-1 con el objetivo de evaluar la producción de metabolitos de la fermentación. Para ello, la cepa se cultivó en frascos Erlenmeyer conteniendo jugo de manzana esterilizado y sin aroma, y los compuestos químicos producidos durante la fermentación en cultivo agitado (200 min-1) y estático (sin agitación) se determinaron. Los resultados mostraron que la agitación del medio de cultivo incrementa la producción de alcoholes superiores (hasta 591,0 mg/L) comparado al cultivo estático, mientras que por el contrario, la producción de ácido acético, etil acetato y glicerol (260,0 ± 11,0 mg/L, 196,0 ± 10,0 mg/L y 2,6 ± 0,2 g/L) resultaron ser mayores que en cultivo agitado (222,0 ± 8,0 mg/L, 96,0 ± 4,5 mg/L y 1,8 ± 0,2 g/L) respectivamente. Cultivos bacth realizados en biorreactor con un flujo de aire de 25 L/h reportaron una tasa de crecimiento (µ) de 0,17 h-1, producción de etanol (12,5 ± 2,0 g/L) y otros compuestos típicamente producidos durante la fermentación alcohólica. La concentración de oxígeno disuelto en el medio de fermentación afecta su metabolismo así, cantidades insuficientes de oxígeno provocaría un metabolismo respirofermentativo. Los mejores resultados en términos de calidad organoléptica de la bebida fermentada en lo referente al aroma, sabor y olor se obtuvieron en la fermentación en cultivo estático. El control de la aireación del medio de fermentación puede ser usado para controlar la síntesis de compuestos químicos de impacto sensorial en la producción de bebidas fermentadas.

The influence of aireation on the fermentative activity of Kloeckera apiculata RIVE 9-2-1 was studied in order to evaluate the production of metabolites of the fermentation. To achieve this, the strain was cultured in Erlenmeyer flasks containing sterilized and aroma removed apple juice, and the chemical compounds produced during fermentation in shaken (200 min-1) and static (without agitation) cultivation were determined. The results showed that the agitation of the culture medium increases production of higher alcohols (till 591.0 mg/L) compared to static cultivation, whereas on the contrary, the production of acetic acid, ethyl acetate and glycerol (260.0 ± 11.0 mg/L, 196.0 ± 10.0 mg/L y 2.6±0.2 g/L) were higher compared to shaken cultivation (222.0 ± 8.0 mg/L, 96.0 ± 4.5 mg/L and 1.8 ± 0.2 g/L) respectively. Batch cultivations carried out in bioreactor with air flux of 25 l/h reported a growth rate (µ) of 0.17 h-1, production of ethanol (12.5 ± 2.0 g/L) and other compounds typically produced during alcoholic fermentation. The concentration of dissolved oxygen in the fermentation medium affects its metabolism thus; insufficient amounts of oxygen would provoke a respirofermentative metabolism. The best results in terms of organoleptic quality of the fermented beverage regarding to aroma, taste and flavour was obtained when fermented in static cultivation. The control of aeration during fermentation can be used to control the synthesis of chemical compounds of sensory impact in the production of fermented beverages.

Optimization of feeding strategy for the ergosterol production by yeasts saccharomyces cerevisiae / Optimización de la estrategia de alimentación para la producción de ergosterol por levaduras saccharomyces cerevisiae

Objective of this study was to optimize ergosterol production by yeast strain Saccharomyces cerevisiae with the use of computer controlled feeding of cultivation medium. Baker´s yeasts strain of Saccharomyces cerevisiae originally modified and selected as mutant D7 was further applied in an industrial scale and also in this investigation. Composition of cultivation medium was optimized with the use of a modified Rosenbrock´s method with regard to following components: glucose, yeast extract, ammonium sulphate, potassium dihydrogen phosphate, magnesium sulphate and calcium chloride. Cultivation of yeast culture was performed in 7 L laboratory bioreactor with a working volume of 5 L equipped with a control unit and linked to a computer, with dissolved oxygen tension measurement, oxygen and carbon dioxide analyzers. BIOGENES prototype software was created from the commercial control system Genesis for Windows 3.0 (GFW), from Iconics and CLIPS 6.04 for the PC-Windows platform. From various factors affecting sterol biosynthesis a specific growth rate was chosen. Feed rate was controlled according to mathematical model. In this case it dealt with a design of optimal profile of specific growth rate with consequent calculation of carbon dioxide profile. Sterol concentration in the dry biomass increased from 1.0 % up to 3 %.

El objetivo de este estudio fue optimizar la producción de ergosterol por una cepa de levadura Saccharomyces cerevisiae, controlando la alimentación de medio de cultivo por computadora. La cepa de levadura panadera Saccharomyces cerevisiae originalmente modificada y seleccionada como mutante D7 fue posteriormente utilizada a escala industrial y también para esta investigación. La composición del medio de cultivo fue optimizada usando el método modificado de Rosenbrock respecto a los siguientes componentes: glucosa, extracto de levadura, sulfato de amonio, fosfato dihidrógeno de potasio, sulfato de magnesio y cloruro de calcio. El cultivo de las células de levadura se llevó a cabo en un biorreactor de laboratorio de 7L con un volumen de trabajo de 5L, equipado con una unidad de control conectada a una computadora, con medición de la tensión de oxígeno disuelto y analizadores de oxígeno y dióxido de carbono. Un software prototipo BIOGENES fue creado a partir del sistema de control comercial Genesis para Windows 3.0 (GFW), de Iconics y CLIPS 6.04 para la plataforma de PC-Windows. A partir de varios factores que afectan la biosíntesis de esterol se escogió una tasa específica de crecimiento. La tasa de alimentación se controló mediante un modelo matemático. En este caso, se trató con un diseño de perfil óptimo de tasa de crecimiento específico con un consecuente cálculo del perfil de dióxido de carbono. La concentración de esterol en la biomasa seca se incrementó desde 1,0% hasta 3%.

Growth, sporulation and production of bioactive compounds by Bacillus subtilis R14

The physiology of B. subtilis R14 was investigated in minimal medium under excess-oxygen and oxygen-limited conditions. Growth and efficient sporulation could be achieved in excess-oxygen culture on medium with readily metabolizable carbon and nitrogen sources, which allowed high growth rate and high biomass yield. A short transition phase between the exponential growth and sporulation could be attained by formulating a medium with a well-balanced C/N ratio. Under oxygen-limitation, but in the presence of essential nutrients (i.e. excess-nutrient cultivation), B. subtilis R14 produced bioactive compounds, which showed activity against several phytopathogenic bacteria. Under anaerobic condition, the organism did not grow neither through fermentation nor anaerobic respiration. However, addition of pyruvate to the medium allowed its growth through fermentation and anaerobic respiration. The knowledge acquired in this work could be relevant both for the design of a production process as well as for the formulation of an effective commercial biocontrol product.

A fisiologia de B. subtilis R14 foi investigada em meio mínimo em condições de excesso e limitação de oxigênio. Crescimento e esporulação eficientes foram obtidas em culturas com excesso de oxigênio em meio contendo fontes de carbono e nitrogênio de fácil assimilação, que permitiram alta taxa de crescimento e alto rendimento em biomassa. Uma fase de transição curta, entre o crescimento exponencial e a esporulação, pode ser obtida pela formulação de um meio com razão C/N balanceada. Sob limitação de oxigênio, mas em presença de nutrientes essenciais, B. subtilis R14 produziu compostos bioativos. Os compostos apresentaram atividade contra várias bactérias fitopatogênicas. Sob condição de anaerobiose, o microrganismo não cresceu, nem através de fermentação nem de respiração anaeróbica. A adição de piruvato ao meio permitiu o crescimento, tanto através de fermentação como de respiração anaeróbica. O conhecimento adquirido neste trabalho é relevante tanto para o projeto do processo de produção quanto para a formulação de um produto comercial eficiente para biocontrole.

Should Strengthen Cognizing and Teaching to the Deceleration Phase of Single Cell Organisms Growth Curve in Batch Cultivation / 微生物学通报

The growth curve of single cell organisms in batch cultivation could divide into 6 phases, lag phase, acceleration phase, log phase, deceleration phase, stationary phase, and death phase, based on specific growth rate during cultivation process. There were significantly differences between deceleration phase and the other phases in cell growth, substrate consumption, product formation, and genes express profile. The deceleration phase was highly important to fermentation process. However, cognizing and teaching to the deceleration phase had been considerably weakened since a long period. So it should be strengthened.